The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/0b1544ce99f9ff26421e81079109e745659b6612

commit 0b1544ce99f9ff26421e81079109e745659b6612
Author: Christopher Grant <cjgrant@chromium.org>
Date: Thu Dec 21 20:22:50 2017

VR: Use component background image if available.

If a component is downloaded and available, start the UI, but don't
render any browser-related UI until the asset is loaded from disk and
the texture is ready.

If no component is available, draw the original gray-grid background.

Note that currently, we never transition from one background to another.

BUG= 793407 

Cq-Include-Trybots: master.tryserver.chromium.android:android_optional_gpu_tests_rel;master.tryserver.chromium.linux:linux_optional_gpu_tests_rel;master.tryserver.chromium.mac:mac_optional_gpu_tests_rel;master.tryserver.chromium.win:win_optional_gpu_tests_rel
Change-Id: I51cf3719f9557c139cd1fdad8377126ad904d765
Reviewed-on: https://chromium-review.googlesource.com/837600
Commit-Queue: Christopher Grant <cjgrant@chromium.org>
Reviewed-by: Ian Vollick <vollick@chromium.org>
Cr-Commit-Position: refs/heads/master@{#525786}
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/android/vr_shell/gl_browser_interface.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/android/vr_shell/vr_gl_thread.cc
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/android/vr_shell/vr_gl_thread.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/android/vr_shell/vr_shell_gl.cc
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/android/vr_shell/vr_shell_gl.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/BUILD.gn
[add] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/elements/background.cc
[add] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/elements/background.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/elements/ui_element_name.cc
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/elements/ui_element_name.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/model/model.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/test/ui_test.cc
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/test/ui_test.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/ui.cc
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/ui.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/ui_element_renderer.cc
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/ui_element_renderer.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/ui_scene.h
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/ui_scene_creator.cc
[modify] https://crrev.com/0b1544ce99f9ff26421e81079109e745659b6612/chrome/browser/vr/ui_unittest.cc